Neurological soft signs (NSS) are minor neurological abnormalities, including motor, sensory, and inhibitory dysfunction. Schizophrenia and other neuropsychiatric disorders are associated with a higher prevalence of NSS. However, the relationships between NSS and schizophrenia, bipolar disorder, and major depression are unclear.

Dr. Raymond Chan’s team from the Neuropsychology and Applied Cognitive Neuroscience (NACN) Laboratory, Key Laboratory of Mental Health, Institute of Psychology conducted a rigorous study to examine the specificity of NSS among these three clinical groups. They have recruited a total of 120 demographically matched  participants (30 each in schizophrenia, bipolar disorder, major depression, and healthy controls) and evaluated the prevalence of NSS using the Cambridge Neurological Inventory (CNI). They found that significant differences were demonstrated in the total score of NSS, and the subscale scores for motor coordination, sensory integration and disinhibition. Both patients with schizophrenia and bipolar disorder showed more total NSS signs than healthy controls. Patients with schizophrenia also showed more total NSS signs than patients with major depression. Both patients with schizophrenia and patients with bipolar disorder showed more motor coordination signs than healthy controls and patients with major depression. Moreover, compared with healthy controls, patients with schizophrenia showed more disinhibition signs, while patients with bipolar disorder showed more sensory integration signs (p<0.01). They further used discriminant analysis to examine the clinical discrimination of NSS among the three clinical groups and found that 77.5% of correct classification of patients with schizophrenia and bipolar disorder could be discriminated from patients with major depression and healthy controls. 

These findings suggest that although NSS may not be unique to schizophrenia, but these signs were significantly unique to patients with psychotic symptoms. Patients with major depression are comparable to normal controls. These findings may provide further evidence to support the similarity between schizophrenia and bipolar disorder from the dimension of behavioral expression.

This study was supported by the National Science Foundation China Outstanding Young Investigator Award (81088001), the National Key Technologies R&D Programme (2012BAI36B01), the Knowledge Innovation Project of the Chinese Academy of Sciences (KSCX2-EW-J-8), and the Key Laboratory of Mental Health, Institute of Psychology.

The current study entitled "Neurological soft signs discriminate schizophrenia from major depression but not bipolar disorder"was published online by Progress in Progress in Neuro-Psychopharmacology and Biological Psychiatry

Zhao, Q., Ma, Y. T., Lui, S. S. Y., Liu, W. H., Xu, T., Yu, X., Tan, S. P., Wang, Z. R., Qu, M., Wang, Y., Huang, J., Cheung, E. F. C., Paola, D., Chan, R. C. K*. (2013). Neurological soft signs discriminate schizophrenia from major depression but not bipolar disorder. Progress in Progress in Neuro-Psychopharmacology and Biological Psychiatry, 43, 72-78.